If a character makes you feel scared psychologically, even if its just how they are drawn list here.

Mine is Kirakishou in Rozen Maiden, she doesn't seem to know anything about personal space in some chapters, looks like someone that would say, "I will eat you nice and slowly my precious," she is a cannibal (kinda), and despite being a doll, eats the souls of people. *Twilight Zone theme plays